1. Field of the Invention
The present invention relates to a piston type compressor with an improved valve mechanism, adapted for use in a unit for air-conditioning a vehicle passenger compartment, and more particularly, to a piston type compressor with suction and discharge valve mechanisms free from irregular vibrations which cause noise in the air-conditioning circuit and abnormal resonances in the vehicle.
2. Description of the Related Art
Many piston type compressors, such as a swash plate type compressor and a wobble plate type compressor, are known. For example, U.S. Pat. No. 4,403,921 to Kato et al discloses a swash plate type compressor with double-acting reciprocatory pistons and suction and discharge valve mechanisms employing suction and discharge reed valves. The known swash plate type compressor of U.S. Pat. No. 4,403,921 includes a cylinder block having therein a plurality of cylinder bores serving as compression chambers for permitting double-acting pistons to be reciprocated therein to compress a refrigerant gas. The ends of the cylinder block are closed by front and rear housings, via valve plates, respectively, so that suction and discharge chambers are formed in each of the front and rear housings. The suction chambers are fluidly communicated with the compression chambers through suction ports formed in the valve plates and suction reed valves arranged on inner side of respective valve plates, and the discharge chambers are fluidly communicated with the compression chambers through discharge ports formed in the same valve plates and discharge reed valves arranged on an outer side of respective valve plates. The valve plates are also formed with inlet ports for permitting a refrigerant gas returning from the outer air-conditioning circuit to flow into the suction chambers, and outlet ports for permitting a compressed refrigerant gas to flow from the discharge chambers into the air-conditioning circuit.
With the above-described swash plate operated piston type compressor, the movement of the suction and discharge reed valves from the open position thereof apart from the valve plates to the closed position thereof in close contact with the valve plates, and vice versa, takes place in response to a pressure differential between the suction and discharge chambers and the compression chambers of the plurality of cylinder bores. Therefore, a change in the amount of the refrigerant gas throughout the air-conditioning circuit including the compressor as well as a change in a flow resistance of the gas pumped into the compression chambers from the suction chambers and discharged from the compression chambers into the discharge chambers during operation of the compressor, causes an abnormal vibration of the suction and discharge reed valves. The abnormal vibration of the valves is added to the normal oscillatory motions of the same valves, and as a result, complicated and irregular vibrations of the suction and discharge reed valves occur. The complicated vibrations are transmitted to an evaporator and a gas condenser in the air-conditioning circuit, via a suction gas piping and a discharge gas piping, and cause noise from the evaporator and the gas condenser.
Further, in recent light-weight cars, the body of the car per se is brought into a state of resonance with the vibrating evaporator and the condenser, and produces a resonant noise in the passenger compartment of the car.